Sound generators are today used in many different types of applications. Thus, in particular, they are often used in warning or alarm devices, in which a warning signal can be outputted in a controlled manner as a function of a detected event. Thus such alarm devices are used, for example, as fire alarm systems, burglar alarm systems, transit alarm systems, entry alarm systems, or also to monitor machines or vehicles, to record specific events by means of a sensor and to trigger and correspondingly generate appropriate alarm signals.
Since the users of such warning or alarm devices rely on the reliable functioning of the device, it is essential that in particular the sound generator also operates reliably in such a warning or alarm device.
From DE 100 20 862 A1 a sound generator of an alarm device has become of known art, in which the sound generator, here designated as a signal generator, is associated with a checking device, which receives and processes the acoustic signal emitted by the sound generator, or forwards it to an evaluation unit, which then evaluates the acoustic signal. Here the checking device is simply tuned to the signal outputted from the signal generator, which in the case of a sound generator is the acoustic signal. Thus the possibility of an error exists, if, instead of the warning signal from the sound generator that is being monitored, another signal from a neighbouring signal generator is detected, for example, or a signal that is incorrect in some other respect. In such cases it would be assumed that the signal originated from the signal generator being monitored, and the signal generator would be considered to be fault-free, although in actual fact this would not be the case.
DE 196 33 863 A1 discloses an alarm system for monitoring a plurality of objects, in particular intrusion monitoring of houses, with a plurality of alarm systems associated with one object; these alarm systems include a sensor, which is designed to detect an event triggering an alarm. The alarm system also includes a transmission unit, which forwards the alarm signal identifying the alarm state and an identification signal identifying the object to other alarm systems, so that where there is a large number of neighbouring alarm systems the alarm state of one alarm system is fed in so that the residents can take appropriate measures. However, no fault monitoring and/or monitoring of the reliable functioning of a sound generator takes place in this case.
DE 37 17 369 A1 discloses a method and a device for monitoring a space in which an additional signal generator is used; this outputs a signal that is received by the detector of the system, and the detector output port signal and the signal controlling the signal generator are compared. On the basis of this comparison optimal operation of the device is derived and any improper manipulation is excluded. However, no explicit fault monitoring and/or monitoring of the reliable functioning of a sound generator takes place in this case, since the signal from the sound generator is not included in the check, but just the detector signal, which activates the sound generator if an incident occurs.